FIG. 26 shows a perspective view of an existent linear guide device. The linear guide device comprises a guide rail 51 and a slider 60. The slider 60 comprises a slider main body 52, end caps 53 and side seals 54. Then, the linear guide device, a not illustrated guide rail-side member and a not illustrated slider-side member constitute a table apparatus. The not illustrate guide rail-side member is, for example, a substructure to which the guide rail is secured and the not illustrated slider-side member is, for example, a table secured to the slider main body.
The guide rail 51 is extended in one direction and has rolling element grooves 55 on both lateral side wall surfaces in the longitudinal direction. The guide rail 51 is attached to the guide rail-side member by using rail attaching screw holes 56 by means of not illustrated bolts. The slider-side member is attached to the slider main body 52 by using four slider main body attaching screw holes 84 by means of not illustrated bolts.
The slider main body 52 is of a substantially U-shaped cross section with a concave portion in the inside.
When the end caps 53 and the side seals 54 are attached to both longitudinal ends of the slider main body 52, the slider 60 is completed. The end cap 53 and the side seal 54 are integrally attached to the slider main body 52 by using assembling screw holes 85 and not illustrated bolts. Four assembling screw holes 85 are provided on each side of the slider main body 52.
As is well-known so far, rolling elements are loaded in a predetermined circulation channel formed in the slider 60. The slider 60 moves on the guide rail 51 by the rolling motion of the rolling elements between the guide rail 51 and the slider 60 when they conduct endless circulation in the circulation channel.
Description is to be made for a joining member used for attaching the guide rail 51 to the guide rail-side member, a joining member used for assembling the slide 60 and a joining member used for attaching the slider-side member to the slider main body 52, for example, screw.
FIG. 27(a) is an enlarged view of a main portion showing a state of an attaching screw 21 which is screwed and clamped in a receiving portion of the slider main body 52. In this state, the receiving portion is, for example, an attaching screw hole 84, and the slider-side member 70 is attached to the slider main body 52 by screwing and clamping the attaching screw 21 in the attaching screw hole 84. A state of an assembling screw which is screwed and clamped in the assembling screw hole 85 and a state of a rail attaching screw which is screwed and clamped in a rail attaching screw hole 56 are identical to the attaching screw 21 with respect to the surrounding conditions of the bolt.
As shown in FIG. 27(a), when the screw 21 is screwed into the screw hole 84, a gas reservoir 23 as a gap remains at the bottom of the screw hole. When a table apparatus with a linear guide device is assembled by clamping each screw and put in vacuum or depressurized circumstances, the gas reservoir forms “dead space”. With evacuation of air by a vacuum pump, a small amount of air slowly and gradually passes through a contacting area between the head of the screw 21 and the slider side member 70. The passing air continuously leaks into the vacuum or depressurized circumstances, even though the screw 21 is tightened completely. Accordingly, it takes a considerable time till such leakage stops, that is, till the pressure in the portion of the gas reservoir 23 is equal to the outside pressure. It takes much time, particularly, in a case where the extent of the outside vacuum condition is high. The gas reservoir causing such a problem is present on every portions where members constituting the table apparatus with the linear guide device are joined to each other by combination of screws and screw holes.
Then, for solving the problem, as shown in FIG. 27(b), it has been known a method to remove the accumulated air in the gas reservoir 23 instantly by using a special screw (gas vent bolt) 25. The special screw 25 has a gas vent hole 24 that axially perforates through a central portion.
However, the special screws are expensive and it is not easy to fabricate vent holes to screws of various sizes used for assembling and combining the members that constitute the table apparatus.
Further, as shown in FIG. 28(a), another member 26 is sometimes attached on the slider-side member 29 to which the slider main body 52 is directly attached. In such a case, when the slider-side member 29 is secured to the slider main body 52 by using a special screw 25, for example, with a gas vent hole 24, there remains a sealed space 28 in a counter head to contain the head of the special screw 25. The space 28 is tightly sealed to the outside by another member 26 and also forms a gas reservoir. Accordingly, even though the special screw 25 is used, both the gas reservoir 23 at the bottom of the screw hole and the space 28 constitute “dead space”, and a small amount of air leaks into the vacuum circumstance or depressurized circumstance continuously and gradually.
After all, for coping with such a case, users of the linear guide device have to use the expensive special screws 25 and, further, fabricate the gas vent holes 27 to another member 26.
In view of the problems described above, the present invention intends to provide a linear guide device suitable to be used in vacuum or depressurized circumstances, as well as a table apparatus with the linear guide device without using any special screws formed with the gas vent hole.